Table of Contents📚

• What is a function❓
• Declaring a function
• Returning values

Functions🛠️

What is a function❓

A function is a block of code that takes an input and produces an output.

Declaring a function

A function can be declared with the fn keyword.

ℹ️ Functions have to be declared outside of the main function and before they are called.

fn function_name(param1: Type, param2: Type) {
    // function body
}

Exemple, write a function called hello that says 🔔 TIME TO EAAT x times:

fn hello(x: i32) {
    for _ in 0..x {
        println!("🔔 TIME TO EAAT");
    }
}

fn main() {
    hello(5);
}

Output:

🔔 TIME TO EAAT
🔔 TIME TO EAAT
🔔 TIME TO EAAT
🔔 TIME TO EAAT
🔔 TIME TO EAAT

Returning values

Functions can return a value with the return keyword.

For example, create a function isEven that returns true or false depending on whether the input is even or odd:

fn is_even(x: i32) -> bool {
   return x % 2 == 0
}

ℹ️ We have to specify the return type of a function with the -> after the function name and parameters.

The % operator is called the modulo operator. It returns the remainder of an euclidean division. So if we have a number x and we want to know if it is even, we can use the modulo operator to check if the ramainder of its euclidiand division by 2 is 0.

We can now use the isEven function to print even numbers from 1 to 10:

fn main() {
    for i in 1..11 {
        if is_even(i) {
            println!("{} is even", i);
        }
    }
}

Output:

2 is even
4 is even
6 is even
8 is even
10 is even

---

Home 🏠 - Next Section ⏭️

---

Course created by SkwalExe and inspired by Dcode